1. Field of Invention
The present invention relates generally to brakes and in particular to an apparatus for adjusting a cam actuated brake.
2. Description of Related Art
Brakes for rotating disks are well known. A common brake for such disks is known as a caliper brake. A caliper brake provides a pair of brake pads disposed on either side of the rotating disk. Each brake pad may be attached to an arm at a proximate end. The arms are rotatable about an intermediate axis and actuated by an actuator between the distal ends thereof.
An example of a cam actuated caliper brake assembly is shown in U.S. Pat. No. 4,121,697 to Kobelt et. al. the entirety of which is incorporated herein by reference. U.S. Pat. No. 4,121,697 to Kobelt et al. provides a wedge or cam between a pair of followers on the distal ends of the arms.
A present difficulty with disk brakes arises due to wear of the brake pads. As the brake is used, the brake pads are worn or abraded away. As the thickness of the brake pads is reduced due to wear, the arms of the caliper brake are required to pivot through a greater angle to cause the brake pads to contact the disk. The actuator is therefore required to displace the distal ends of the arms by a greater distance. In the case of a cam actuated caliper brake assembly, the wedge or cam will be required to be displaced by a greater distance by the actuator. Unfortunately, many actuators in use for brakes typically have a relatively short stroke due to the primary design considerations being applicable force and modulation as opposed to stroke length.
In addition, many actuators have a spring return or release whereby the actuator returns to a fully retracted position when the brake is not being applied. In cam actuated brakes, such as in U.S. Pat. No. 4,121,697 to Kobelt et al., the retraction of the actuator may cause the wedge or cam to be retracted from engagement upon the following surfaces. In this retracted position, the contact surfaces between the following surfaces and the wedge or cam may become fouled or misaligned from each other.
One solution to the problem of brake pad wear is to provide an actuator having a longer stroke. While this solution will enable the brake pads to contact the disk over a larger range of brake pad wear, this solution will not prevent the disengagement of the wedge or cam from the cam followers. Such actuators may also be more expensive than those traditionally used and suffer from deficiencies in applicable force and modulation.
Another solution is to provide a link with an adjustable length between the actuator and the wedge or cam. The length of such a link may be adjusted so as to remove any slack caused by brake pad wear. Such an adjustable link requires that the length be adjusted periodically so as to ensure proper operation of the brake. The process of adjusting such a link, however, requires that the brake not be in operation during the time of the adjustment. Because the brake may be used as an emergency safety device in some operations, this will require that all of the surrounding equipment similarly be stopped during the adjustment. The resulting shutdown time may be quite expensive in some industries, such as, for example, oil drilling.
What is desirable is an adjusting cam actuated brake assembly that may be rapidly adjusted to compensate for brake pad wear.